Here at Digital Anarchy HQ, we have experimented with many screen solutions during development of the Primatte Chromakey plugin. Here are our thoughts about choosing a screen material. Our suggestions are meant as a starting point, not a final solution, so please test your setup to determine which chromakey material surface delivers the best results for your job.
Chroma Key fabric is a foam-backed fabric manufactured by Velcro. It comes in 60" wide rolls, is sold by the yard, and is available in blue or green. The fabric is very travel/wrinkle resistant and you can easily roll or fold it. The foam absorbs light, which cuts down reflection on your model. When our subjects are photographed against the blue or green Chromakey fabric, we have experienced very little color spill and Primatte quickly pulls a great mask. You can buy this material through photo supply houses like Film Tools and Chroma-key.com.
We generally do not feel that chromakey paper works well. Many papers are glossy with a very reflective surface which can cause color spill. The exception is Savage Paper Tech Green #46. This chromakey paper has a nice flat finish which gives very little reflection and allows easy lighting. For a full length pose, we recommend this paper. It can hang horizontally in a long roll, is light to carry, rolls back up easily, and is quite portable.
A disadvantage to paper is that it's delicate and prone to damage. It's easy to replace but that potentially gets expensive. You also need a way to hang the paper.
Read more in our AnarchyJim blog post titled What Material to Use for Greenscreen?" This is a very detailed overview of using chromakey paper, in particular Tech Green #46.
There are many other options for chromakey material. Each has pros and cons, just like the fabric and paper. For instance:
Paint: You can buy house paint in bright medium green or bright medium blue. Just go to any Home Depot or Kellys Paint. We painted sheets of wood with green for some of our earliest experiments. Paint works ok if it is VERY flat, and it is easy to clean or touch up.
This is an inexpensive solution, however, you get what you pay for. The background can be dull and may not light very well. There are specialty chroma-blue and chroma-green paint available which surely work better but of course are more expensive.
Twist-flex: A reversible, double-sided fabric screen in green and blue. If you work on location, these are great for portability because they are lightweight and two-sided (green/blue). The twist-flex also doesn't develop dark wrinkles which often throw off the color scheme of chromakey software.
The problem with the twist-flex screens is they are usually polyester. That material tends to be somewhat reflective and not very light absorbent, which may generate a lot of color spill. The only twist-flex we tested is from the FlexDrop2 products by Photoflex. It's adequate, but we wouldn't recommend it unless there's no other options. Digital Juice also has a twist-flex green screen.
If you are using chromakey paper or fabric, a question that arises is how to hang the material. Here are some thoughts:
- If you can find a good seamstress, many folks have the fabric sewn together. If done right, this becomes almost seamless.
- Avoid tape if possible. It will be a different color than the fabric, which is a potential small headache. You can buy chromakey tape but it is expensive and generally not reusable.
- Stapling will work if the material is pulled taunt. The downside to stapling is the risk that the fabric will tear, and you will probably have to re-staple everything occasionally as the fabric stretches/shrinks over time.
- You can attach C-clamps to the fabric, run a rail through the C-clamps, and then pull the fabric taunt along the rail.
- You can build a wood frame, wrap the fabric around the frame like a painting canvas, and staple gun the fabric to the frame.
Step Four : What is color spill?.